Modern microprocessors are formed of various stages that receive instructions, execute the instructions, and provide results of the instructions. Many modern architectures are based on an out-of-order (OOO) implementation in which instructions can be executed out of order and the results are later committed to an architectural state of the processor in order.
To realize such out of order operation, the processor pipeline can be segmented into various stages. At a conclusion of processing of instructions in such stages, a retirement stage may operate to confirm that the results of the execution are valid, i.e., are not speculative or based on incorrect data, and that no faults or exceptions occurred. In many processor architectures, in each retirement cycle the entire retirement logic is active such that all associated data is read from all associated arrays and the fall retirement logic is invoked for each instruction. All this activity is aimed at producing a guarantee signal and performing retirement related operations including event calculation and prioritization.
However, in most cycles no events occur and therefore there is no need to calculate the events. As such, there is significant power consumption that is not needed for proper operation.